The present invention relates to a semiconductor device module and, more specifically, relates to a novel module employing an insulated metal substrate (IMS), one or more power circuit boards, interconnects and other components that are arranged in a novel manner.
Known semiconductor device modules are used for housing a plurality of interconnected semiconductor chips. The chips may be of the same or of diverse kind and may be mounted on a heatsink or other substrate within a common housing having terminal electrodes which extend from the housing.
In a power application, such as for a motor control circuit or similar functions, both high power devices, from which heat must be removed, as well as low power devices, which do not require heatsinking, are employed. Typically, the heatsinking may be provided by mounting the devices on an IMS which is enclosed in a module housing. Such substrates and modules are described in U.S. Pat. No. 5,408,128, issued Apr. 18, 1995 in the name of the inventor of the present application and assigned to International Rectifier Corporation, the present assignee. However, when both high power and low power devices are required for an application, the inclusion of low power devices on an IMS greatly increases the cost of the module. Alternatively, the high power devices are included within the IMS module and the low power devices are mounted externally in other modules, thus greatly increasing the footprint of the circuit as well as requiring additional interconnections between the high and low power devices.
It is therefore desirable to provide a device package which houses both the high and low power devices and in which the package size is reduced, and the number and lengths of interconnects are minimized.
The present invention provides an xe2x80x9cadaptable planar modulexe2x80x9d (APM), namely a new packaging concept for motor control and similar functions. The package is especially suited for low cost and small motor control systems, though the basic concept can be extended to larger, higher power systems.
The APM of the invention includes a minimum IMS substrate suitable for the power devices and other devices. The IMS substrate may support an input bridge, an inverter, and other components and sits beneath an open cavity of a printed circuit board (xe2x80x9cPCBxe2x80x9d). The PCB and the IMS substrate are potted in a molded shell that is provided with connectors. The PCB provides a low cost platform for the low power devices that do not require heatsinking and thus need not be situated on the IMS substrate. Interconnecting the IMS and the PCB are standard wire bonds that connect the semiconductor die on the IMS substrate and those on the PCB.
The invention thus eliminates redundant interconnects, provides cost savings and improves reliability. Specifically, the partitioning of the devices and the IMS size reduction save cost. The size reduction and direct bond to the die also reduce the unit IMS cost by eliminating the need for special plating and by allowing for a thinner IMS.
The APM of the present invention typically includes an IMS, a printed circuit board, a support base or shell, power terminals, and grounding terminals. Environmental considerations may also be taken into account. An external control PCB with keypad and I/O terminals, a cover, and a heatsink may also be included.
The IMS substrate of the APM may include an inverter, one or three phase inputs, a thermistor, a negative buss shunt and a ground fault shunt. Epoxy or solder die attachments may be used. The substrate may be suitable for any or all of 0.18, 0.37 or 0.75 kilowatt applications. The size of the substrate is, for example, 1.2 inches by 0.8 inches. Also, pollution 1 standard compliance with a coating may be provided, as may be 2500 V dielectric isolation.
The shell or package of the APM may include a molded shell that supports the IMS, the power PCB and the cover. The shell, for example, has a footprint of about 2.83 inchesxc3x975.12 inches (72xc3x97130 mm) with extended terminals. Three or four, for example, M4 mounting screws may be used for earth, panel, internal and heatsink grounding, respectively. The package preferably has a low profile of 0.375 inches, as an example, and may be made of high temperature and high strength plastic.
The power PCB of the APM may typically be a single PCB that can include a drive circuit, protection circuits, SMPS, filters, buss capacitors, soft-charge, terminals and a control board interface connector. The PCB is generally, for example, about 5.2 inchesxc3x972.6 inches. Preferably, the PCB is formed of two layers, though four layers are also possible. The top side of the PCB may include an SMD and a through-hole. The bottom side of the PCB may include a SMD of, preferably, up to 1.3 inches. The PCB may also include pollution 1 spacing with both sides coated or potted.
The power terminals are typically LMI or Schneider type. As an example, a three output motor is used as well as a two or three input line. The PCB may be grounded to earth at the input end, and preferably meets UL 508C specifications at 600V. The power terminals may be soldered to the power PCB.
Preferably, the APM conforms to a pollution level 2 requirement, though level 3 conformity may be provided if select control pins are managed. The APM may also be protected from vibration, shock and other mechanical stresses.
The primary grounding of the APM is preferably the heatsink. A motor shield may be clamped to the heatsink for EMC specification compliant grounding and for motor grounding to the heatsink. An input side mounting screw may connect the line earth, panel and panel ground to the heatsink and to the internal ground. A jumper from the heatsink that internally grounds the EMC terminal may also be provided.
A control PCB may be included in the APM or may be provided externally and interface with a connector and ribbon cable. The control PCB may preferably include a microprocessor, xe2x80x9cshrubberyxe2x80x9d, keypad and a Wago I/O connector. The control PCB typically mechanically snaps into the cover and is connected by flex cable.
A cover may interface with the APM shell and is preferably a molded cover with a product-dependent height. The cover may provide a mechanical and electrical connection to the components, and may include a snap-on coupling to the shell and may permit mounting screws through the shell to the heatsink. The cover may also provide support for the control board and vents for capacitor cooling. Optionally, the cover is UL 50 specification compliant.
An external heatsink serves as the mounting surface for the APM. Three sizes are preferable for the heatsink, all of which preferably have the same footprint, namely an extruded aluminum heatsink for 0.37 kilowatt applications, extruded aluminum for 0.75 kilowatt applications, or an aluminum plate for 0.18 kilowatt applications. The heatsink is preferably sized for providing final power dissipation without using a fan. Typically, three or four tapped holes may be provided to connect the heatsink to the APM. The heatsink may also be mountable to a back panel or to a DIN rail.
The innovative shell design may provide any or all of the following features: location and support of the IMS substrate, optimum contact to the heatsink mounting surface, support of the PCB including wire bond support, space for SMD components on the bottom surface of the PCB, space for both SMD and leaded components on the top side of the PCB. A small depressed cavity above the IMS is provided for the IMS components and is preferably filled with a hi-grade potting compound that contacts the IMS die. The remainder of the package, including the PCB and other components, can thus be covered with a lower cost potting compound.
The shell may also create an external terminal housing, when such a housing is more cost effective than using procured terminals. Alternatively, the shell can create a partitioned area to attach procured terminals to the PCB.
Other, larger components such as buss capacitors, filter capacitors, and inductors may require special mounting and interconnects. These components may be attached to the PCB and may be allowed to protrude from the potting compound, or they may be placed atop an additional PCB. The additional PCB may be a co-planar extension of the first PCB or may be situated on a second level, depending on the size, number and cost of the component mounting, and will differ from one product to another. It may be advantageous, in some packages, to attach the larger components, such as the buss capacitors, to the bottom of the package and include an appropriate cover.
The top surface of the package may also accommodate a control key board which leads to the PCB.
Other applications, such as for appliances, may not require terminals and may incorporate lower cost fast-on connectors. Applications such as industrial controllers may add extra functions as well as higher power and mechanical structures.
The adaptability of the Adaptable Planar Module allows for flexibility in the design of products by modifying the layout of either the PCB or the IMS without any significant change in hard tooling. Other changes can also be made by building the shell mold with a changeable insert for the IMS substrate cavity or by incorporating a multiple upper mold cavity to accommodate higher walls for double boards, special connectors, an optional keyboard, and the like.
Thus, the APM provides a low cost package that allows for fuller system integration in a single module. Specific system functions may include: an inverter, input bridge, current sensing, short circuit and overtemperature protection, driver circuits, input/output filters, PFC, brake, a control microprocessor, and a keyboard.
In accordance with the invention, a semiconductor device module includes a support base that has an opening which extends from its top surface to its bottom surface. A planar, thermally conductive substrate extends across the support base opening and has a bottom surface that is situated at or below the bottom surface of the support base for contacting an external heatsink. One or more semiconductor devices are mounted on a top surface of the thermally conductive substrate. At least one circuit board is arranged above and is spaced from the top surface of the support base and has an opening that is situated above the thermally conductive substrate, and one or more other semiconductor devices are mounted on a top surface of the circuit board. At least one bonding pad area is arranged at a periphery of the opening in the circuit board and is electrically connected to the semiconductor devices of the circuit board. One or more bonding wires connect the semiconductor devices of the thermally conductive substrate to the bonding pad.
Other aspects of the invention include a motor drive module and a micro-converter module.
Plural, interconnected semiconductor devices may be mounted on thermally conductive substrate. The thermally conductive substrate may be an IMS. A power die or an inverter circuit may be mounted on the thermally conductive substrate.
The support base may include raised portions which extend above the support base top surface and which surrounds the opening in the circuit board to form a cavity above the thermally conductive substrate. The cavity may be filled with a high grade potting material, and at least part of a region atop the surface board may be filled with a low grade potting material. Further raised portions in the support base may support the circuit board.
Integral terminals, mounted atop the circuit board, or procured terminals, formed in a raised portion of the support base, may provide electrical connections and are electrically connected with the devices of the circuit board. Another circuit board may be mounted above and spaced from the circuit board, or may be mounted co-planar with the circuit board, and has further devices mounted on its surface. A keyboard may be mounted atop one of the circuit boards, and additional devices may be mounted on the bottom surface.
The present invention may be modified to provide a xe2x80x9cflexible power assemblyxe2x80x9d (FPA), namely a new packaging concept for motor control and similar functions. The package is especially suited for low cost and small motor control systems, though the basic concept can be extended to larger, higher power systems.
The FPA of the present invention includes an IMS suitable for the power devices and other devices. The IMS may support an input bridge, an inverter, and other components and may sit beneath an open cavity of a printed circuit board (xe2x80x9cPCBxe2x80x9d). The PCB and the IMS are potted in a molded cover that is provided with connectors. The PCB provides a low cost platform for the low power devices that do not require heatsinking and thus need not be situated on the IMS. The IMS and the PCB may be interconnected by standard wire bonds that connect the semiconductor die on the IMS and other devices and components on the PCB. An FPA according to the present invention includes a heatsink that supports the substrate and the PCB.
In accordance with this invention, a semiconductor device module includes a heatsink directly supporting a thermally conductive substrate. One or more semiconductor devices are mounted on the thermally conductive substrate and are electrically connected to other devices that are mounted on a PCB. The PCB is situated above the thermally conductive substrate, and may include a cavity. The cavity in the PCB extends from the top surface of the PCB to its bottom, and is positioned above the thermally conductive substrate so that the semiconductor devices on the thermally conductive substrate are exposed. One or more bonding wires may provide the electrical connection between the semiconductor device or devices on the thermally conductive substrate and the device or devices on the PCB.
The cavity may be made wide enough so that the thermally conductive substrate protrudes through the cavity entirely, and the edges of the cavity on the underside of the PCB may be placed in contact with the top of an insulation element, which on its bottom side is in contact with the top of the heatsink.
In yet another embodiment, the cavity in the PCB may also be made narrow enough so that the edges of the cavity on the underside of the PCB will rest on the thermally conductive substrate resulting in the closing of the cavity by the body of the thermally conductive substrate.
The semiconductor device module according to the foregoing may further include a molded cover to reside on the top surface of, and over the cavity in, the PCB, such that the molded cover will enclose a space above the thermally conductive substrate. The space may then be filled with a potting compound.
In another embodiment, no cavity is provided in the PCB. Instead, an enclosure means surrounding the semiconductor device or devices is provided. The enclosure means meets the top of the thermally conductive substrate and the underside of the PCB thereby providing an enclosed space over the semiconductor device or devices, thus eliminating the need for a molded cover. Potting compound may then be contained in the enclosed space. Electrical connection by means of a via may then be made between the semiconductor device or devices and a device on the PCB.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.